In my opinion neither of those amps are "nice" on the top. I was an MF dealer and used a 4B for an hour in my system before I just had to remove it. Very metallic sounding to my ear. Too bad too I really wanted it, they are well built and as it was a trade in I could have gotten it cheap. I settled on CJ SS amps. I first got the 100WPC MF2100. Nice. I then got a MF2500- 250WPC and put the 2100 in the closet. I then bi-wired the 2500. Big improvement. I then decided hey these two amps both have the same gain,input impedance and sensitivity. I then implemented a horizontal bi-amp. Again another level of improvement. Not subtle either, especially in image and soundstage. Read Rodman's link too, it's good.
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